1. Technical Field
The present invention relates to a liquid jet head and a liquid jet recording apparatus each of which ejects liquid from a nozzle hole to record an image or a character on a recording medium.
2. Related Art
Conventionally, as an apparatus which jets liquid (ink) onto a recording medium, a liquid jet recording apparatus which jets ink droplets from a plurality of nozzle holes of an ink chamber toward a recording medium has been known. Such a liquid jet recording apparatus includes one that is provided with an ink jet head in which a so-called ink jet method is employed.
A head chip is provided in the ink jet head. The head chip is provided with a piezoelectric actuator on which a plurality of long grooves filled with ink are formed. Electrodes are provided on opposite side walls of each of the long grooves. By applying a predetermined drive voltage to these electrodes, the side walls are deformed, and a capacity inside each of the long grooves changes. As a result, ink droplets are ejected from the nozzle holes toward a recording medium.
Various techniques for increasing the number of nozzle holes have been proposed for the purpose of improving the density of a character or an image recorded on a recording medium. For example, JP 2004-209796 A discloses a technique that enables high density recording by arranging two head chips in a stack to thereby double the number of nozzle holes.
A more detailed description will be made on the basis of FIG. 10.
FIG. 10 is a transverse sectional view of an ink jet head of a conventional example (FIG. 12 of JP 2004-209796 A).
As illustrated in FIG. 10, an ink jet head 110 includes two head chips 101 which are arranged in a stack. Each of the head chips 101 includes a lower substrate 111, an upper substrate 113, a channel portion 115 which is formed between the lower substrate 111 and the upper substrate 113, a nozzle plate 102 which is adhered to the front of the channel portion 115, a wiring board 103 which is adhered to the outer surface of the lower substrate 111, and a driver IC 104 which is mounted on the wiring board 103.
The channel portion 115 is surrounded by the lower substrate 111, the upper substrate 113, and two walls (not shown) which are interposed between the lower substrate 111 and the upper substrate 113 and made of piezoelectric bodies.
The two head chips 101 are laminated with each other in such a manner that the upper substrates 113 of the respective head chips 101 face each other and the lower substrates 111 thereof are located on outer side. The wiring boards 103 are adhered to the outer surfaces of the respective two lower substrates 111. That is, the two head chips 101 are interposed between the two wiring boards 103. The driver ICs 104 are mounted on the inner surfaces of the respective wiring boards 103. Therefore, an area located opposite to the liquid ejection side of the two head chips 101 is surrounded by the two wiring board 103.
Each of the driver ICs 104 mounted on each of the wiring boards 103 inputs therein a control signal from an external circuit such as a control circuit through two connectors 105 and a wiring 106, and generates a drive signal for selectively driving each of the channel portions 115. The drive signal generated by each of the driver ICs 104 is supplied to the corresponding channel portion 115 through a driver wiring 107. The two walls made of piezoelectric bodies are deformed according to the drive signal, which causes the capacity of the channel portion 115 to change. Accordingly, ink filled inside the channel portion 115 is ejected from a nozzle.
Next, another example that enables high density recording will be described on the basis of FIG. 11.
FIG. 11 is a schematic perspective view of a liquid jet head of another conventional example.
As illustrated in FIG. 11, a liquid jet head 120 includes a two-row head chip 123, two circuit boards 124 and 125 which supply a drive signal to the two-row head chip 123, a relay printed circuit board 126 which supplies a control signal to the circuit boards 124 and 125, and four flexible substrates 127, 128, 131, and 132.
The two-row head chip 123 includes two nozzle rows which are formed by adhering together two piezoelectric actuators 121 and 122 which are made of piezoelectric bodies.
In the four flexible substrates 127, 128, 131, and 132, the flexible substrates 127 and 128 are used for electrically connecting the circuit boards 124 and 125 and the two-row head chip 123 to each other. On the other hand, the two flexible substrates 131 and 132 are used for electrically connecting the relay printed circuit board 126 and the two circuit boards 124 and 125 to each other.
The relay printed circuit board 126 is provided with an external device connecting connector 133 which inputs therein a control signal from an external circuit. The relay printed circuit board 126 supplies the input signal to the two circuit boards 124 and 125 through the two flexible substrates 131 and 132.
The two circuit boards 124 and 125 are provided with driver ICs 134 and 135, respectively. Each of the driver ICs 134 and 135 generates a drive signal for driving the two-row head chip 123 according to the input control signal. A drive signal generated by the driver IC 134 is supplied to the upper piezoelectric actuator 121 through the flexible substrate 127. On the other hand, a drive signal generated by the driver IC 135 is supplied to the lower piezoelectric actuator 122 through the flexible substrate 128.
Therefore, the liquid jet head 120 which includes the two-row head chip 123 requires the two circuit boards 124 and 125, the single relay printed circuit board 126, and the four flexible substrates 127, 128, 131, and 132.
In JP 2004-209796 A, the wiring boards 103 are placed on the outside of the lower substrates 111 of the respective head chips 101 so as to largely protrude toward the side opposite to the liquid ejection side. Therefore, the weight of the ink jet head 110 increases, and there is a limit to make the ink jet head 110 thin. In addition, the capacity and the volume of the ink jet head 110 increase. As a result, a carriage and a member of a drive system for driving the carriage become large, thereby disadvantageously increasing the size of the entire apparatus.
Further, disadvantageously, the mass of the carriage which loads thereon a plurality of ink jet heads 110 increases, and a large load is thereby applied on the drive system for driving the carriage.
Further, since the area located opposite to the liquid ejection side of the two head chips 101 is occupied by the wiring boards 103, unfortunately, the area cannot be utilized for another device. In addition, since the two connectors 105 are provided, restriction on the layout of connection between the wirings 106 and an external circuit such as a control circuit disadvantageously increases.
In the conventional example illustrated in FIG. 11, the two circuit boards 124 and 125, the four flexible substrates 127, 128, 131, and 132, and the single relay printed circuit board 126 are placed in an area located opposite to the liquid ejection side. Therefore, unfortunately, there is a limit to reduce the thickness of this area.
Further, the number of components is large, an assembly step for assembling the components becomes complicated and long, and the cause of failure also increases.